Abstract

The use of phase has a long standing history in optical image processing, with early milestones being in the
field of pattern recognition, such as VanderLugt's practical construction technique for matched filters, and (implicitly)
Goodman's joint Fourier transform correlator. In recent years, the flexibility afforded by phase-only spatial light
modulators and digital holography, for example, has enabled many processing techniques based on the explicit encoding
and decoding of phase. One application area concerns efficient numerical computations. Pushing phase measurement to
its physical limits, designs employing the physical properties of phase have ranged from the sensible to the wonderful, in
some cases making computationally easy problems easier to solve and in other cases addressing mathematics' most
challenging computationally hard problems. Another application area is optical image encryption, in which, typically, a
phase mask modulates the fractional Fourier transformed coefficients of a perturbed input image, and the phase of the
inverse transform is then sensed as the encrypted image. The inherent linearity that makes the system so elegant mitigates
against its use as an effective encryption technique, but we show how a combination of optical and digital techniques can
restore confidence in that security. We conclude with the concept of digital hologram image processing, and applications
of same that are uniquely suited to optical implementation, where the processing, recognition, or encryption step operates
on full field information, such as that emanating from a coherently illuminated real-world three-dimensional object.

Item Type:

Book Section

Additional Information:

Some ideas in this manuscript have benefitted from discussions with Damien Woods. The research leading to
these results has received funding from Science Foundation Ireland under the National Development Plan, and the
European Community’s Seventh Framework Programme FP7/2007-2013 under grant agreement no. 216105 (Real
3D).